Generate API files as interfaces for go-gin server (#17784)

* add feature to generate only interface files

* generate sample

* add workflow file foe go gin service

* add workflow file foe go gin service

* add workflow file foe go gin service

* update samples

samples/server/petstore/go-gin-api-server-interface-only/go/api_user.go

@@ -0,0 +1,51 @@
+/*
+ * OpenAPI Petstore
+ *
+ * This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+ *
+ * API version: 1.0.0
+ * Generated by: OpenAPI Generator (https://openapi-generator.tech)
+ */
+
+package petstoreserver
+
+import (
+	"github.com/gin-gonic/gin"
+)
+
+type UserAPI interface {
+
+
+    // CreateUser Post /v2/user
+    // Create user 
+     CreateUser(c *gin.Context)
+
+    // CreateUsersWithArrayInput Post /v2/user/createWithArray
+    // Creates list of users with given input array 
+     CreateUsersWithArrayInput(c *gin.Context)
+
+    // CreateUsersWithListInput Post /v2/user/createWithList
+    // Creates list of users with given input array 
+     CreateUsersWithListInput(c *gin.Context)
+
+    // DeleteUser Delete /v2/user/:username
+    // Delete user 
+     DeleteUser(c *gin.Context)
+
+    // GetUserByName Get /v2/user/:username
+    // Get user by user name 
+     GetUserByName(c *gin.Context)
+
+    // LoginUser Get /v2/user/login
+    // Logs user into the system 
+     LoginUser(c *gin.Context)
+
+    // LogoutUser Get /v2/user/logout
+    // Logs out current logged in user session 
+     LogoutUser(c *gin.Context)
+
+    // UpdateUser Put /v2/user/:username
+    // Updated user 
+     UpdateUser(c *gin.Context)
+
+}